1. Field of the Invention
This invention relates to an apparatus and method for quickly and economically forming water ice or CO.sub.2 snow over a load of perishables disposed within an elongated storage container such as a semitrailer body or a shipping container. High pressure, highly atomized fog-like jets of liquid CO.sub.2 and H.sub.2 O are produced over a load to be chilled and the finely atomized fog-like discharges are relatively positioned so as to rapidly commingle and produce ice and/or CO.sub.2 snow precipitation over the load.
2. Description of Related Art
Various different methods and apparatuses for forming ice and/or CO.sub.2 snow heretofore have been known, such as those disclosed in U.S. Pat. Nos. 3,762,176, 4,111,362, 4,838,039, 5,154,064 and 5,295,368. Ice is typically about a 50/50 mixture of water and CO.sub.2 and forms temperatures of about +20.degree. F. to +32.degree. F. CO.sub.2 snow, on the other hand, is 100% CO.sub.2 and has a temperature of about -110.degree. F. When making ice by mixing water and liquid C.sub.2, it is desirable to utilize the lowest ratio of liquid CO.sub.2 to water, and to achieve the highest conversion of water to ice, so as to improve the economics and efficacy of the system.
The apparatus disclosed in U.S. Pat. No. 3,762,176 forms ice within a divergent nozzle terminal end of an elongated water supply tube and the cryogenic fluid is discharged under pressure into the terminal end nozzle at a rate which must be precisely controlled to prevent water freezing within the terminal end nozzle before discharging therefrom. The system disclosed in U.S. Pat. No. 4,111,362 discharges precisely positioned jets of liquid CO.sub.2 into a mixing chamber in such a manner that the kinetic energy of all of the liquid CO.sub.2 jets is dissipated. U.S. Pat. No. 4,838,039 discloses an apparatus wherein ice is produced from aqueous liquids by directly contacting the aqueous liquids with a liquified refrigerant.
My earlier U.S. Pat. Nos. 5,154,064, 5,295,368 and 5,505,055 disclose apparatus for forming ice by mixing liquid CO.sub.2 and H.sub.2 O in various ways. The apparatus disclosed in my U.S. Pat. No. 5,505,055 is particularly adapted for forming ice particles over a load of perishables disposed within an insulated storage or shipping container or the like by discharging opposing spray jets of liquid CO.sub.2 and water toward each other. However, the apparatus of my aforementioned prior patents are not effective in maximizing the cooling capability of the liquid CO.sub.2. Specifically, these prior art systems are not capable of approaching the desired production efficiency of one pound of water ice for each pound of liquid CO.sub.2 consumed.
My earlier U.S. Pat. No. 5,775,111 discloses an apparatus and method for discharging CO.sub.2 snow and ice along a generally horizontal path over and onto a load within an elongated insulated container from one partially opened end of the container. This patent discloses the discharging of liquid CO.sub.2 inside a duct at pressures approaching 300 psi and spray discharging water at generally 60 psi pressure for commingling of the water and liquid CO.sub.2 in order to form water ice or a mixture of water ice and CO.sub.2 snow. However, this apparatus and method has the disadvantage of spraying the contents of the entire trailer or container from only one end and, thus, is not fully effective to cover all of the product being chilled.
Furthermore, the apparatuses of the prior art are assembled inside the container space, such as along the ceiling as disclosed in my U.S. Pat. No. 5,505,055 or adjacent the rear doors as disclosed in my U.S. Pat. No. 5,775,111. As such, the ice and snow making nozzles, piping and the like are subject to damage when struck by packages being shipped or the heavy equipment moving such packages. Embedding the piping and nozzles is disclosed for insulated railroad cars in my co-pending application, Ser. No. 09/167,535, filed Oct. 7, 1998.
Also, various different methods and apparatuses for forming CO.sub.2 snow over perishable loads within elongated shipping containers heretofore have been known. My prior U.S. Pat. Nos. 4,640,460 and 5,398,522 each disclose the advantages of discharging opposing jets of liquid CO.sub.2 against each other and further the additional advantage of lowering the temperature of the pressurized liquid CO.sub.2, immediately before being jet discharged, to the triple point temperature (approximately -69.degree. F. at 75 pounds per square inch absolute).
However, in addition to the first mentioned objective of obtaining maximum water ice production per unit of liquid CO.sub.2 consumed, the prior art also fails to disclose an apparatus, for usage in an elongated shipping container, efficiently operable to form either a CO.sub.2 snow layer or a water ice layer over a load in the shipping container.